| 富里酸-膨润土复合体对氟的吸附特性 |
| 摘要点击 2727 全文点击 1600 投稿时间：2015-09-25 修订日期：2015-11-02 |
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| 中文关键词 富里酸 膨润土 复合体 氟 吸附 |
| 英文关键词 fulvic acid bentonite complex fluorine adsorption |
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| 中文摘要 |
| 采用共沉淀法制备了富里酸-膨润土复合体(FA-BENT),研究了FA-BENT的基本性质及其在不同环境条件下对氟的吸附特性. XRD分析显示,FA-BENT中蒙脱石的(001)面衍射峰强度有所减弱,但其层间距没有明显变化,表明FA-BENT中富里酸主要包被在膨润土外表面. FTIR结果表明,FA-BENT膨润土的矿物组分主要与富里酸表面C=O、—OH等官能团结合,配位体交换、表面络合作用是其主要作用机制. 低pH范围内,升高反应体系的初始pH有利于FA-BENT对氟的吸附; 当初始pH上升至4.50以后,吸附量随pH升高而降低; FA-BENT对氟的吸附也受离子强度的影响,其主要原因可能是"极性"效应; FA-BENT对氟的动力学吸附过程遵循拟二级动力学机制,受化学过程控制(R2=0.9992); 与Freundlich模型相比,Langmuir模型对氟在FA-BENT上的吸附数据具有较高的拟合优度(R2>0.9949). 热力学参数表明,FA-BENT对氟的吸附属于熵驱动的自发吸热反应过程[ΔH为32.57 kJ ·mol-1,ΔS为112.31 J ·(mol ·K)-1,ΔG为-0.65~-1.76 kJ ·mol-1]. |
| 英文摘要 |
| Fulvic Acid-Bentonite (FA-BENT) complex was prepared using coprecipitation method, and basic properties of the complex and sorption properties of fluorine at different environmental conditions were studied. XRD results showed that the d001 spacing of FA-BENT complex had no obvious change compared with the raw bentonite, although the diffraction peak intensity of smectite in FA-BENT complex reduced, and indicated that FA mainly existed as a coating on the external surface of bentonite. Some functional groups (such as C=O, —OH, etc.) of FA were observed in FA-BENT FTIR spectra, thus suggesting ligand exchange-surface complexation between FA and bentonite. Higher initial pH values of the reaction system were in favor of the adsorption of fluorine onto FA-BENT, while the equilibrium capacity decreased with the increase of pH at initial pH≥4.50. The adsorption of fluorine onto FA-BENT was also affected by ionic strength, and the main reason might be the "polarity" effect. The adsorption of fluorine onto FA-BENT followed pseudo-second-order kinetic model and was controlled by chemical process(R2=0.9992). Compared with the Freundlich model, Langmuir model was apparently of a higher goodness of fit (R2>0.9949) for absorption of fluorine onto FA-BENT. Thermodynamic parameters indicated that the adsorption process of fluorine was an spontaneously endothermic reaction, and was an entropy-driven process(ΔH 32.57 kJ ·mol-1, ΔS 112.31 J ·(mol ·K)-1, ΔG -0.65--1.76 kJ ·mol-1). |
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